Abstract: Systems and methods for removing a DC offset from an orthogonal frequency division multiplexed (OFDM) signal transmitted over a plurality of subcarrier frequencies. The system includes a receiver. The system further includes a high pass DC component filter configured to reduce a DC component of the orthogonal frequency division multiplexed signal, the high pass DC component filter shaping noise in the orthogonal frequency division multiplexed signal which results in a non-uniform power spectral density of the noise across the plurality of subcarrier frequencies. The system further includes a noise whitener configured to compensate for the noise shaping by the high pass DC component filter by normalizing the non-uniform power spectral density of the noise across the plurality of subcarrier frequencies.

Abstract: Systems and methods for detecting data in a multiple input/multiple output signal. The method includes receiving a first signal associated with a first data value and a second signal associated with a second data value. A distance value between the received second signal and each possible second data value is calculated. Coordinates for a hypothetical first signal in light of a first possible second data value are calculated, and the first coordinate value is quantized to a nearest constellation point. A distance value between the received second signal and each possible second data value is calculated using the calculated constellation points. A determination is made of a log-likelihood ratio based on the determined distance values.

Abstract: In a method for generating a physical layer (PHY) data unit for transmission via a communication channel, a plurality of information bits to be included in the PHY data unit are received, and a number of orthogonal frequency division multiplexing (OFDM) symbols that are needed to include the plurality of information bits after encoding with a low density parity check (LDPC) encoder is determined. One or more of a, b, c, and d are performed according to a set of rules so that a receiving device can determine a number of information bits in the PHY data unit based on i) an indication of the number of OFDM symbols, and ii) the set rules: a) adding padding bits and/or shortening bits prior to encoding with the LDPC encoder, b) removing shortening bits after encoding with the LDPC encoder, c) removing parity bits after encoding with the LDPC encoder, d) repeating information and/or parity bits after encoding with the LDPC encoder. The plurality of information bits are encoded using the LDPC encoder.

Abstract: Systems and methods are provided for whitening noise of a received signal vector in a multiple-input multiple-output (MIMO) transmission or storage system. The whitening filter may be designed to whiten an interference component of the received signal vector, where the interference component is derived from modeling transmitter and receiver imperfections as a first coupling between MIMO transmitter outputs and a second coupling between MIMO receiver. The whitening filter may be computed based on the covariance matrix of the interference component.

Abstract: A plurality of training signal sets are transmitted. Each training signal set includes information sufficient to determine a channel estimate corresponding to a communication channel from a first station to a second station. A refined channel estimate is determined based on reception of the plurality of training signal sets.

Abstract: A method for processing a preamble of a data unit transmitted via a communication channel includes receiving a signal via a plurality of antennas, applying a plurality of distinct steering vectors to the received signal to generate a plurality of respective outputs, and using the plurality of outputs to perform at least one of carrier sensing and symbol timing synchronization associated with the preamble.

Abstract: A circuit for use in a complementary Golay sequence generator or in a complementary Golay sequence correlator includes an input configured to receive an input signal, a set of delay elements, including delay elements corresponding to respective delays of 1, 2, 4, 8, 16, 32, and 64, and a set of multipliers interconnected with the input and the set of delay elements. The set of multipliers is configured to apply weight factors, and the weight factors define the sequence 1,1,?1,1,?1,1,?1. The circuit also includes a pair of outputs configured to output, in response to the input signal, one of (i) a pair of complementary Golay sequences or (ii) a pair of correlation output signals, using (a) the set of delay elements and (b) the set of weight multipliers.

Abstract: In a method for beamforming in a multiple input multiple output (MIMO) communication system, a data unit is received from a communication device via a MIMO communication channel, and it is determined whether the data unit satisfies one or more selection criteria. Further, when it is determined that the data unit satisfies the one or more selection criteria, the data unit is selected to be used in developing a steering matrix for transmitting data units to the communication device.

Abstract: A system including a receiver to receive, over a wireless channel, a packet including a preamble portion that includes a plurality of training fields and a first signal field and a controller to generate a first estimate of the wireless channel based on one or more of the plurality of training fields, and decode the first signal field based on the first estimate. Subsequent to decoding the first signal field, the controller re-encodes the first signal field to generate a second signal field. The controller verifies whether the first signal field was properly decoded by comparing the second signal field to the first signal field prior to being decoded. In response to the first signal field being correctly decoded, the controller generates a second estimate of the wireless channel based on the first signal field as decoded. The second estimate is usable to refine the first estimate.

Abstract: Systems and methods for removing a DC offset from an orthogonal frequency division multiplexed (OFDM) signal transmitted over a plurality of subcarrier frequencies. The system includes a receiver. The system further includes a high pass DC component filter configured to reduce a DC component of the orthogonal frequency division multiplexed signal, the high pass DC component filter shaping noise in the orthogonal frequency division multiplexed signal which results in a non-uniform power spectral density of the noise across the plurality of subcarrier frequencies. The system further includes a noise whitener configured to compensate for the noise shaping by the high pass DC component filter by normalizing the non-uniform power spectral density of the noise across the plurality of subcarrier frequencies.

Abstract: A transmitter beamforming technique for use in a MIMO wireless communication system determines (i) a partial description of a reverse channel without determining a full dimensional description of the reverse channel and (ii) a partial description of a forward channel without determining a full dimensional description of the forward channel. A correction matrix is developed from the partial description of the reverse channel and a partial description of the forward channel. The correction matrix is used to process signals to be transmitted via the forward channel, and a steering matrix is used to perform beamforming in the forward channel.

Abstract: A wireless network comprises R client stations that respectively generate simultaneous uplink transmission (SUT) data, where R is an integer greater than one. An access point (AP) receives SUT data from each of the R client stations during an SUT period.

Abstract: A method includes determining a mean square error ?h2 of an estimate h of a communication channel, and receiving a data symbol y. The received data symbol y corresponds to a data symbol x transmitted over the communication channel. The method also includes determining a likelihood value for a bit in the transmitted data symbol x. Determining the likelihood value for the bit in the transmitted data symbol x includes calculating a quantity according to ? - ? y - hx ? 2 ? z 2 + ? h 2 ? ? x ? 2 , where ?z2 is a noise power associated with the communication channel. The method also includes calculating the likelihood value for the bit in the transmitted data symbol x as a function of the calculated quantity.

Abstract: A Viterbi decoder module includes a branch metric module configured to calculate branch metrics corresponding to a continuous phase modulated signal. Each of the branch metrics corresponds to a respective path between stages of the Viterbi decoder module. A path metric module is configured to calculate a first cost metric associated with the first state of the next stage based on the first branch metric and the second branch metric, and calculate a second cost metric associated with the second state of the next stage based on the third branch metric and the fourth branch metric. A traceback module is configured to determine a maximum likelihood path between stages of the Viterbi decoder based on the first cost metric and the second cost metric. The Viterbi decoder module is configured to output decoded data based on the maximum likelihood path.

Abstract: In a method for detecting a packet type of an orthogonal frequency division multiplexing (OFDM) data unit detected in a communication channel, a first estimate and a second estimate of a transmitted symbol are determined for each of at least some of a plurality of OFDM tones in an OFDM symbol of the data unit. A first distance and a second distance are determined between a received symbol and, respectively, the first estimate and the second estimate scaled by a channel response estimate corresponding to the OFDM tone. A first total distance is determined based on a mathematical summation of the first distances over the plurality of OFDM tones. A second total distance is determined based on a mathematical summation of the second distances over the plurality of OFDM tones. The packet type is determined based at least on the first total distance and the second total distance.

Abstract: In a method for transmitting information in a wireless local area network (WLAN), a plurality of different data streams corresponding to a plurality of different devices are orthogonally multiplexed onto a single symbol stream without using channel state information corresponding to a plurality of channels between a transmitting device and the plurality of different devices. One or more transmit streams are generated using the single symbol stream.

Abstract: A method selects a codebook for transmit beamforming. The method constructs an estimated channel matrix based on a codebook, selects a channel submatrix from the estimated channel matrix, calculates a selection matrix from the channel submatrix; and assigns a steering matrix based on the selection matrix. The method may construct an estimated channel matrix, select a channel submatrix, and calculate a selection matrix for each of multiple codebooks, then select an optimal codebook. The steering matrix is assigned based on the optimal codebook. The steering matrix may be used in steering a transmitted packet. The method may also calculate a post-MIMO equalizer signal-to-noise ratio for a data stream, based on the estimated channel matrix and the selected codebook. A related system is also disclosed. Other embodiments are provided, and each of the embodiments described herein can be used alone or in combination with one another.

Abstract: Systems and methods are provided for directing radiated energy from a transmitting device towards a receiving device using multiple antennas. Channel weights, representing signal attenuation and a phase rotation induced by a transmission medium, are determined at a transmitting device. A set of steering weights are determined based on applying an iterative linear transform to an initial value of the steering weights, where the linear transform depends on the determined channel weights. A final value of the steering weights is applied to an input signal to produce a transmit signal, and the transmit signal is transmitted using multiple antennas.

Abstract: A bias current utilized in a unit of a radio frequency (RF) receiver device of a network interface is controlled. A modulation scheme utilized in a packet being received by the network interface is determined. It is determined, based on the determined modulation scheme, whether a level of the bias current should be changed. When it is determined that the level of the bias current should be changed, a control signal to change the level of the bias current is generated.

Abstract: A transmitter device includes a controller configured to generate a first field and a second field. The first field is at least one of a packet synchronization information field or a frame boundary indication field, the second field is a channel estimation field starting after the first field ends. The controller is configured to generate the second field at least in part by generating a first channel estimation sequence (CES) symbol and a second CES symbol. At least one of i) a sequence in the first field serves as a cyclic prefix of the first CES symbol, ii) a beginning portion of the second CES symbol serves as a cyclic postfix of the first CES symbol, or iii) an ending portion of the first CES symbol serves as a cyclic prefix of the second CES symbol.